feat: outline directive implementation example

Signed-off-by: Hidde Beydals <hidde@hhh.computer>

internal/directives/copy_directive.go

@@ -0,0 +1,53 @@
+package directives
+
+import (
+	"context"
+	"errors"
+	"fmt"
+)
+
+func init()  {
+	// Register the copy directive with the builtins registry.
+	builtins.RegisterStep(&copyDirective{})
+}
+
+// copyDirective is a directive that copies a file or directory.
+type copyDirective struct{}
+
+// copyConfig is the configuration for the copy directive.
+type copyConfig struct {
+	// InPath is the path to the file or directory to copy.
+	InPath string `json:"inPath"`
+	// OutPath is the path to the destination file or directory.
+	OutPath string `json:"outPath"`
+}
+
+// Validate validates the copy configuration, returning an error if it is invalid.
+func (c *copyConfig) Validate() error {
+	var err []error
+	if c.InPath == "" {
+		err = append(err, errors.New("inPath is required"))
+	}
+	if c.OutPath == "" {
+		err = append(err, errors.New("outPath is required"))
+	}
+	return errors.Join(err...)
+}
+
+func (d *copyDirective) Name() string {
+	return "copy"
+}
+
+func (d *copyDirective) Run(_ context.Context, stepCtx *StepContext) (Result, error) {
+	cfg, err := configToStruct[copyConfig](stepCtx.Config)
+	if err != nil {
+		return ResultFailure, fmt.Errorf("could not convert config into copy config: %w", err)
+	}
+	if err = cfg.Validate(); err != nil {
+		return ResultFailure, fmt.Errorf("invalid copy config: %w", err)
+	}
+
+	// TODO: add implementation here
+
+	return ResultSuccess, nil
+}

internal/directives/registry.go

@@ -1,6 +1,17 @@
 package directives
 
-import "fmt"
+import (
+	"fmt"
+	"maps"
+)
+
+// builtins is the registry of built-in steps.
+var builtins = StepRegistry{}
+
+// BuiltinsRegistry returns a registry of built-in steps.
+func BuiltinsRegistry() StepRegistry {
+	return maps.Clone(builtins)
+}
 
 // StepRegistry is a map of step names to steps. It is used to register and
 // retrieve steps by name.

internal/directives/step.go

@@ -2,6 +2,7 @@ package directives
 
 import (
 	"context"
+	"encoding/json"
 
 	"k8s.io/apimachinery/pkg/runtime"
 )
@@ -72,3 +73,23 @@ type Step interface {
 	// Run executes the step using the provided context and configuration.
 	Run(ctx context.Context, stepCtx *StepContext) (Result, error)
 }
+
+// configToStruct converts a Config to a (typed) configuration struct.
+func configToStruct[T any](c Config) (T, error) {
+	var result T
+
+	// Convert the map to JSON
+	jsonData, err := json.Marshal(c)
+	if err != nil {
+		return result, err
+	}
+
+	// Unmarshal the JSON data into the struct
+	err = json.Unmarshal(jsonData, &result)
+	if err != nil {
+		return result, err
+	}
+
+	return result, nil
+}
+